partially, to storage of the fruit for 5 days at 20 C. Nevertheless, ethylene degreening did not enhanceoff-avor perception or accumulation of off-avor volatiles, nor had any effect on levels of health pro-moting compounds such as vitamin C, total phenols and avonoids, or antioxidant-activity of citrus juice.We conclude that although ethylene affects peel color break, it is probably not involved in regulation ofinternal ripening processes in citrus fruit and, therefore, does not impair internal fruit quality.

cteric fruit, ethylene plays a key role in governingal and biochemical changes that occur during ripen-ng color break, softening, and accumulation of sugars,a volatiles, vitamins, etc. (Lelievre et al., 1997; Barry and2007). In contrast, citrus fruit are non-climacteric, i.e.,al ripening is not accompanied by rises in respiratione production rates (Eaks, 1970). However, exposure toethylene has been shown to stimulate various ripening-cesses, such as destruction of the green chlorophylld accumulation of orange/yellow carotenoids, in citrus(Stewart and Wheaton, 1972; Barmore, 1975; Purvisre, 1981; Rodrigo and Zacarias, 2007). In the light ofvations, degreening practices involving exposure of theylene at concentrations of 25L L1 for about 72h atere developed, in order to accelerate peel color changeer the fruitmore acceptable formarketing (Grierson and60; Cohen, 1978). In particular, commercial degreen-nts are especially important for early varieties, in order

to extend their marketing seasons, and for fruit grown in warm,tropical climates, such as those in Florida or India, where natu-ral color development is relatively weak (Wardowsky et al., 2006;Porat, 2008).

Nevertheless, despite widespread knowledge of the effect ofethylene on peel color development, it is not yet known whetherexogenous ethylene regulates other biochemical changes associ-ated with internal ripening of citrus fruit, as it does in climactericfruit (Goldschmidt, 1998). The commondogma is that, in contrast toits effects on peel color change, ethylene has only relatively minoreffects on ripening processes in citrus esh, but this has neveryet been examined systematically. On the contrary, several linesof evidence suggest that ethylene may regulate various processesrelated to internal ripening. First, it is well known that exposureto ethylene accelerates respiration and ethylene-production ratesof citrus fruit, and these rates are indicators of activation of bio-chemical changes, such as breakdownof sugars and acids that serveas respiratory substrates (Aharoni, 1968; Vines et al., 1968; Eaks,1970). Second, previous studies have shown that ethylenedegreen-ing affects variousmetabolic pathways in citrus esh. For example,ethylene degreening decreased acidity levels in Mosambi oranges(LadaniyaandSingh, 2001), increasedproductionof aromavolatilesin green lemons (Norman and Craft, 1968), and slightly affectedaccumulation and composition of carotenoid pigments in the esh

xposure to exogenous ethylene, e.g., during ethylene degreen-rocesses in the peel tissue, such as destruction of the greenorange/yellow carotenoids. Nonetheless, it is not yet knownal ripening processes in citrus esh. To address this question,ne on taste, aroma, perceived avor, and nutritional qualitynges, Star Ruby grapefruit and Satsuma mandarins. Expo-k, and respiration and ethylene production rates in all citrushad no effect on juice total soluble solids and acid contents,

nd composition of juice aroma volatiles. Moreover, sensoryening did not affect the avor of oranges and grapefruit, butof mandarins; the latter change could be attributed, at least

r or not to degreen citrus fruit is not simple, and isy various circumstances, such as market demands andurations of storage and shelf life (Pool and Gray, 2002).last few years, because of increased competition in

kets and increasing public awareness of the nutri-ts of horticultural produce, growers and consumersg increasing importance to the avor and nutritional

through November of the 2009 and 2010 growing sea-cases, fruit were harvested at the beginning of natural, and were collected directly from the harvest bins athouse. For taste score evaluations, additional mandarinre also tested, including Michal, Odem, Or, Mor, and

e degreening

re selected for uniformity of size and color, and divideds, which were exposed, respectively, to air or to ethy-48, or 72h. They were exposed to ethylene by placing-L airtight sealed plastic tanks, into which appropriatepure ethylene were injected, to achieve a nal concen-L L1. Ethylene concentrations were veried by gasaphy according to Porat et al. (1999). The tanks werey to ensure that accumulated carbon dioxide levels did0.2%. Control fruit were held in the same storage roomt without ethylene.